C# 4 and .NET 4

440 ❘ ChaPTer 18 Assemblies
Console.SetOut(temp);
}
returnData = writer.ToString();
}
}
}
return returnData;
code snippet DynamicAssembly/CodeDriver.cs
The method CompileAndRun() requires a string input parameter where one or multiple lines of C#
code can be passed. Because every method that is called must be included in a method and a class, the
variables prefix and postfix defi ne the structure of the dynamically created class Driver
and the method Run() that surround the code from the parameter. Using a StringBuilder , the prefix ,
postfix , and the code from the input variable are merged to create a complete class that can be compiled.
Using this resultant string, the code is compiled with the CSharpCodeProvider class. The method
CompileAssemblyFromSource() dynamically creates an assembly. Because this assembly is just needed in
memory, the compiler parameter option GenerateInMemory is set.
If the source code that was passed contains some errors, these will show up in the Errors collection
of CompilerResults . The errors are returned with the return data, and the variable hasError is set
to true .
If the source code compiles successfully, the Run() method of the new Driver class is invoked. The
invocation of this method is done using refl ection. From the newly compiled assembly that can be accessed
using CompilerResults.CompiledType , the new class Driver is referenced by the driverType variable.
Then the InvokeMember() method of the Type class is used to invoke the method Run() . Because this
method is defi ned as a public static method, the BindingFlags must be set accordingly. To see a result of
the program that is written to the console, the console is redirected to a StringWriter to fi nally return the
complete output of the program with the returnData variable.
Running the code with the InvokeMember() method makes use of .NET refl ection.
Refl ection is discussed in Chapter 14.
The Click event of the WPF button is connected to the Compile_Click() method where the CodeDriver
class is instantiated, and the CompileAndRun() method is invoked. The input is taken from the TextBox
named textCode , and the result is written to the TextBlock textOutput .
private void Compile_Click(object sender, RoutedEventArgs e)
{
var driver = new CodeDriver ();
bool isError;
textOutput.Text = driver.CompileAndRun(textCode.Text, out isError);
if (isError)
{
textOutput.Background = Brushes.Red;
}
}
c o d e s n i p p e t D y n a m i c A s s e m b l y / D y n a m i c A s s e m b l yW i n d o w. x a m l . c s
Now you can start the application; enter C# code in the TextBox as shown in Figure 18 - 8, and compile and
run the code.
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